Method for alloy-electroplating group IB metals with refractory metals for interconnections

ABSTRACT

An electroplated metal alloy including at least three elements. A multilayer interconnection structure that includes a substrate that is an interior of the interconnection structure, a conductive seed layer exterior to the substrate, and an electroplated metal alloy layer including at least three elements exterior to the conductive seed layer. A multilayer interconnection structure formed on a substrate, that includes a barrier layer, and a conductive seed layer, wherein the improvement includes an electroplated metal alloy layer including at least three elements. A method for forming a multilayer interconnection structure that includes providing a substrate, depositing a conductive seed layer, and electroplating a metal alloy layer including at least three elements exterior to the conductive seed layer.

CROSS-REFERENCE TO RELATED APPLICATION

The application is a Continuation of co-pending application applicationSer. No. 10/228,539, filed Aug. 27, 2002 by applicants Grant M. Kloster,et al. entitled “METHOD FOR ALLOY-ELECTROPLATING GROUP IB METALS WITHREFRACTORY METALS FOR INTERCONNECTIONS.”

BACKGROUND

1. Field

Circuit structures interconnecting individual devices of a circuit.

2. Relevant Art

One direction in improving integrated circuit technology is to reducethe size of the components or devices on a chip, permitting an increasednumber of devices on the chip. The reduction in size of the devices onan integrated circuit chip requires reductions in the widths andthicknesses of the interconnections that connect the devices on thechip.

At present, the combination of the interconnect's reducedcross-sectional area with the electrical current requirements of thetransistors result in large current densities within the interconnect.It is known that large current density can cause migration of some ofthe interconnect material (ref. F M D'Heurle and A Gangulee, Thin SolidFilms 25, p. 531 (1975)).

Migration of the interconnect material has been generally accepted to bethe result of electrons colliding with the atoms within theinterconnect. The collisions occasionally cause atoms to dislodge andmove in the direction of the electron flow via one of three routes:interstitially, along grain boundaries, or along the free surface. Ifthe migration flow of atoms away from the interconnect is greater than aflow of source atoms to the interconnect, a void will form. Growth ofthe void will eventually result in an opening being formed in theinterconnect. The ability of the interconnect material to resist thisfailure mode is referred to as the electromigration resistance.Electromigration resistance is a primary factor limiting interconnectmaterials longevity. One way to increase performance, reliability, andpower consumption of integrated circuit interconnections is by improvingthe electromigration lifetime.

Where three grain boundaries meet, a triple point junction is formed.Such junctions are randomly dispersed throughout the interconnection andextend in a variety of directions that define potential inlet and outletroutes for displaced copper atoms during current flow. As electricalcurrent flows through the interconnection, copper atoms are displaced bythe electrons. These displaced copper atoms accumulate in the grainboundaries that are downstream of the current and travel along the grainboundaries in the general direction of the current. At grain boundaryjunctions that have fewer upstream inlets than downstream outlets, avoid may develop at that grain boundary junction over time as copperatoms erode form the junction.

FIG. 1 schematically illustrates a copper interconnection and shows anumber of junctions created by adjacent copper crystals. Interconnection70 is formed, in this example, by copper crystal 72, copper crystal 74,copper crystal 76, copper crystal 78, and copper crystal 80. Grainboundary junction 82 is formed by the meeting of inlet grain boundary84, outlet grain boundary 86, and outlet grain boundary 88, thedesignation of inlet and outlet being dictated by the indicateddirection of the flow of electrons. With one upstream inlet and twodownstream outlets, more copper atoms can be expected to leave junction82 through two downstream outlets 86 and 88 then are supplied tojunction 82 through one upstream inlet 84. With more copper atoms beingremoved from junction 82 within interconnection 70 than are beingsupplied to junction 82 from its upstream source, here inlet grainboundary 84, void 90 will eventually develop in interconnection 70 atjunction 82.

Modern interconnections are made principally of a polycrystalline metalconsisting of copper, aluminum, or an aluminum alloy. Electromigrationresistance of these metals may not be sufficient in future generationsof integrated circuits due to the increased current density.

Several techniques have been developed to improve the electromigrationlifetime of an interconnection. These techniques include improvedtexture, interlayers to limit void size, and interconnections ofmultiple layers of material.

The introduction of refractory metals into integrated circuits has beenhindered by the inability to deposit the alloys using electrodepositionfrom an aqueous solution. It is not currently possible to directly platerefractory metals from an aqueous solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of grain boundaries of coppercrystals in a copper interconnection.

FIG. 2 is a cross-section of a tantalum-nitride or titanium-nitrideunderlayer on an interlayer dielectric in accordance with an embodimentof an interconnection stack.

FIG. 3 is the interconnection stack of FIG. 2 after the furtherprocessing of patterning a tantalum, tungsten, cobalt, or titaniuminterlayer in accordance with an embodiment of an interconnection stack.

FIG. 4 is the interconnection stack of FIG. 3 after the furtherprocessing of patterning a seed layer in accordance with an embodimentof an interconnection stack.

FIG. 5 is the interconnection stack of FIG. 4 after the furtherprocessing of electroplating a metal alloy in accordance with anembodiment of an interconnection stack.

FIG. 6 is a graph showing resistivity versus nickel concentration incopper-nickel-tungsten co-plated films.

FIG. 7 is an SEM/EDS spectrum of copper-nickel-tungsten co-plated films.

FIG. 8 is a graph showing nickel and tungsten concentrations incopper-nickel-tungsten co-plated films versus tungsten concentration insolutions (mole per liter).

FIG. 9 is a graph showing nickel and tungsten concentrations incopper-nickel-tungsten co-plated films versus nickel concentrations insolutions (mole per liter).

FIGS. 10 and 11 show SIMS depth profiling of nickel and tungstenconcentrations in the copper-nickel-tungsten co-plated films: FIG. 10before annealing, and FIG. 11 after annealing four hours at 425° C. innitrogen.

FIG. 12 shows an XRD spectrum of copper-nickel-tungsten co-plated film.

The features of the described embodiments are specifically set forth inthe appended claims. The embodiments are best understood by referring tothe following description and accompanying drawings, in which similarparts are identified by like reference numerals.

DETAILED DESCRIPTION

An interconnection is disclosed that, in one embodiment, includes ametal alloy formed, for example, on a substrate of an integrated circuitchip.

In one embodiment, there is disclosed a technique to enable theelectrodeposition of a group IB metal (for example, copper, silver, orgold) with a refractory metal (for example, tungsten, molybdenum,titanium, etc.) using an aqueous solution compatible with currentintegrated interconnect circuit technologies.

In one embodiment, a technique is described that details the uses ofunder-potential deposition of a refractory metal in conjunction withelectrodeposition of group IB metals (copper, silver, and/or gold) toproduce an alloy of the constituent metals. The alloy can contain one ormore of each of the following components, a refractory metal, a group IBmetal, and an iron like metal (for example, iron, nickel, or cobalt).

A common method of utilizing interconnections in integrated circuitsincludes, but is not limited to, as part of the multilayerinterconnection structure or interconnection stack. Examples includeplacing the primary interconnection material, such as for example,copper, between titanium and/or titanium nitride (TiN) or betweentantalum (Ta) and/or tantalum nitride (TaN). The titanium or tantalummaterials act, in one sense, as diffusion barriers between the primaryinterconnection material and other layers above or below the primaryinterconnection material.

Reference is made to FIGS. 2-5 to illustrate an interconnection stackand its manufacturing according to one embodiment. The interconnectionstack will connect, for example, individual devices on a chip or signalsto or from the chip. A typical chip might have interconnection stacksmade up of five or more layers, each interconnection stack separatedfrom other interconnection stacks by pre-metal dielectric (PMD) orinterlayer dielectric (ILD) material. Interconnections, in the contextof circuit structures, include layer or lines (of interconnection stackmaterial) coupled to contact points including circuit devices (e.g.,transistors, capacitors, resistors) or other interconnection layers orlines.

One process used to form interconnections (interconnection stacks),particularly copper interconnections, is a damascene process. In adamascene process, a trench is cut in a dielectric material and filledwith interconnection material (e.g., interconnection stack material) toform the interconnection. A via may be in the dielectric beneath thetrench with a conductive material in the via to couple theinterconnection (interconnection stack) to a contact point (e.g., anunderlying circuit device or interconnection). In one damascene process(a “dual damascene process”), the trench and via are each filled withthe interconnection material (interconnection stack material).

In one embodiment, the interconnect material is deposited usingelectrodeposition, because of its unique ability to plate trenches andvias at higher rates than the field. In this embodiment, theinterconnect material may include a group IB metal (for example, copper,silver, or gold), alloyed with nickel, iron, or cobalt, and a refractorymetal such as tungsten (W), molybdenum (Mo), tantalum (Ta), or titanium(Ti).

FIGS. 2-5 describe the formation of an interconnection stack accordingto an embodiment to a contact point on a substrate, such as, forexample, a semiconductor (e.g., silicon) substrate that may have aplurality of devices formed in and on the substrate. The interconnectionstack described may be a TaN/Ta/Cu seed layer/ternary metal alloy.(FIGS. 2-5 are not drawn to scale, and are not meant to show therelative thicknesses of the layers.)

FIG. 2 shows the substrate after patterning tantalum-nitride layer 110over PMD, in the case of dielectric material directly over a devicesubstrate, or ILD layer 100. PMD or ILD layer 100 is formed on substrate10 over contact point 50 that may be a circuit device orinterconnection. In one embodiment, to form an interconnection stackhaving a thickness of, for example, about 4500 angstrom to about 5000angstrom, tantalum-nitride layer 110 is deposited to a thickness of, forexample, about 400 angstrom by use of direct current (DC) magnetronsputtering in an atmosphere of argon and nitrogen at a total pressure ofabout five (5) mtorr, with a deposition rate of about 20 angstroms persecond.

In one embodiment, substrate 10 defines an interior of a multilayerapparatus, with PMD or ILD layer 100 formed exterior to substrate 10,with tantalum-nitride layer 110 formed exterior to PMD or ILD layer 100,and exterior to substrate 10.

As shown in FIG. 3, tantalum layer 115 may then be deposited overtantalum-nitride layer 110. In one embodiment, to form aninterconnection stack having a thickness of, for example, about 4500angstroms to about 5000 angstroms, tantalum layer 115 is deposited to athickness of, for example, about 400 angstroms by use of direct current(DC) magnetron sputtering in an atmosphere of argon at a total pressureof about five (5) mtorr, with a deposition rate of about 20 angstromsper second.

In one embodiment, substrate 10 defines an interior of a multilayerapparatus. PMD or ILD layer 100 is formed exterior to substrate 10.Tantalum-nitride or titanium-nitride layer 110 may the be formedexterior to PMD or ILD layer 100 and exterior to substrate 10. Atantalum, tungsten, cobalt, or titanium layer 115 may then be formedexterior to titanium-nitride or tantalum-nitride layer 110, exterior toPMD or ILD layer 100, and exterior to substrate 10. In one embodiment,titanium-nitride or tantalum-nitride layer 110 is optional.

FIG. 4 shows the interconnection stack after the further processing ofdepositing seed layer 120 on the surface of tantalum layer 115. In oneembodiment, seed layer 120 is, for example, a copper material depositedusing sputtering deposition techniques. In one embodiment, thesputtering deposition is carried out in an argon atmosphere having apressure of about 5 mtorr. In one embodiment, the deposition rate isabout 20 angstroms per second. In one embodiment, seed layer 120 has athickness of about 1200 angstroms.

In one embodiment, substrate 10 defines an interior of a multilayerapparatus. PMD or ILD layer 100 is formed exterior to substrate 10.Titanium-nitride or tantalum-nitride layer 110 is formed exterior toexterior to PMD or ILD layer 100, and exterior to substrate 10.Tantalum, tungsten, cobalt, or titanium layer 115 is formed exterior totitanium-nitride or tantalum-nitride layer 110, PMD or ILD layer 100,and exterior to substrate 10. Conductive seed layer 120 is formedexterior to tantalum, tungsten, cobalt, or titanium layer 115, exteriorto titanium-nitride or tantalum-nitride layer 110, exterior to PMD orILD layer 100, and exterior to substrate 10. In one embodiment,titanium-nitride or tantalum-nitride layer 110 is optional.

FIG. 5 shows the interconnection stack after electroplating metal alloylayer 125 over seed layer 120. In one embodiment, metal alloy layer 125is a ternary alloy of three elements. In another embodiment, a firstelement is copper. In another embodiment, a first element is copper anda second element is tungsten. In another embodiment, a first element iscopper, a second element is tungsten, and a third element is nickel. Inanother embodiment, a first element is copper, a second element istungsten, and a third element is selected from iron (Fe), cobalt (Co),and/or nickel (Ni).

In one embodiment, substrate 10 defines an interior of a multilayerapparatus. PMD or ILD layer 100 is formed exterior to substrate 10.Titanium-nitride or tantalum-nitride layer 110 is formed exterior to PMDor ILD layer 100, and exterior to substrate 10. Tantalum, tungsten,cobalt, or titanium layer 115 is formed exterior to titanium-nitride oftantalum-nitride layer 110, exterior to PMD or ILD layer 100, andexterior to substrate 10. Conductive seed layer 120 is formed exteriorto tantalum, tungsten, cobalt, or titanium layer 115, exterior totitanium-nitride or tantalum-nitride layer 110, exterior to PMD or ILDlayer 100, and exterior to substrate 10. Metal alloy layer 125 is formedexterior to seed layer 120, exterior to tantalum, tungsten, cobalt, ortitanium layer 115, exterior to titanium-nitride or tantalum-nitridelayer 110, exterior to PMD or ILD layer 100, and exterior to substrate10. In one embodiment, titanium-nitride or tantalum-nitride layer 110 isoptional.

In another embodiment, the first element is copper, and the secondelement is selected from tungsten (W), molybdenum (Mo), tantalum (Ta),and/or titanium (Ti). In another embodiment, the first element iscopper, the second element is selected from tungsten (W), molybdenum(Mo), and/or tantalum (Ta); and the third element is selected from iron(Fe), cobalt (Co), and/or nickel (Ni). In another embodiment, the firstelement is copper, the second element is selected from tungsten (W),molybdenum (Mo), tantalum (Ta), and/or titanium (Ti); and the thirdelement is selected from iron (Fe), cobalt (Co), and/or nickel (Ni).

In terms of electroplating a metal alloy, in one embodiment, themultiple elements of the alloy are co-plated at the same time.

In one embodiment, three metals (e.g., Cu, Ni, W) are co-plated from anaqueous electrolyte solution using a platinum electrode (as an anode).The solution includes three or more of the following: copper sulfate,copper phosphate, nickel sulfate, nickel phosphate, and sodium tungstate(Na₂WO₄). In another embodiment, the aqueous electrolyte solutionincludes a copper compound that forms copper ions in solution, a nickelcompound that forms nickel ions in solution, and a tungsten compoundthat produces tungsten ions in solution. The pH value of a platingsolution may be adjusted by adding sulfuric acid (H₂SO₄) and/or sodiumhydroxide (NaOH). Under the influence of a current through an anode,(for example, a spiral platinum wire), the copper, nickel, and tungstenions are deposited on seed layer 120, which acts as a cathode.

In one embodiment, at least three metals are co-plated using a directcurrent (DC). In another embodiment, at least three metals are co-platedfrom an aqueous electrolyte solution without the use of a current. Inanother embodiment, at least three metals are co-plated from an aqueouselectrolyte solution using a pulsed current. In one embodiment, at leastthree metals are co-plated using a direct current having a constantcurrent density in a range of about 10 to about 20 milliamps per squarecentimeter. In one embodiment, the voltage increases as the co-platingprogresses to maintain a constant current density.

In another embodiment, there is provided aqueous electrolyte solutionsthat have at least three types of metal ions that are deposited on aseed layer cathode under the influence of an anode when current is runthrough the solution. The first type of ion is copper; the second typeof ion is selected from tungsten, molybdenum, titanium, tantalum,vanadium, niobium, yttrium, zirconium, ruthenium, palladium, halfnium,rhenium, and platinum; and the third type of ion is selected from ofiron, cobalt, and nickel. When a suitable direct current is applied, thethree metal ions are deposited onto the seed layer.

In another embodiment, a copper electrode or a copper anode is placed inan aqueous electrolyte solution that contains at least two metal ions ina solution. When a suitable direct current is supplied to the copperanode, copper ions as well as at least two other types of metal ions aredeposited on the seed layer acting as a cathode. In one embodiment, afirst component of the solution is metal ions selected from tungsten,molybdenum, tantalum, and titanium; and a second component of thesolution is metal ions selected from iron, cobalt, and nickel.

In another embodiment a first anode is made of copper, and a secondanode is made of a material selected from iron, cobalt, and nickel. Inone embodiment, the first anode is copper, and the second anode isnickel, which are deposited in an aqueous electrolyte solutioncontaining at least one other metal ion in solution. In one embodiment,the other metal ion is selected from tungsten, molybdenum, tantalum, andtitanium. In one embodiment, a voltage is applied to the copper anodeand the nickel anode, which produces a current that flows through theelectrolyte solution and deposits copper, nickel, and at least one othermetal ion on the seed layer cathode. In another embodiment, a firstvoltage is applied to the copper electrode, and a second voltage isapplied to the nickel anode, with the seed layer cathode held at areference voltage, in one embodiment, zero volts. The first and secondvoltages are used because of the different reduction potentials ofcopper and nickel, and/or to achieve a similar current flow rate and/orto achieve a similar metal material flow rate onto the seed layercathode.

In another embodiment, there is provided three different metal anodes inan electrolyte solution. A voltage can be applied to the three anodes tocreate a flow of metal ions from the three anodes to a seed layercathode through the electrolyte solution. In one embodiment, the firstanode is made of copper. In a second embodiment, the first anode is madeof copper, and the second anode is made of nickel. In anotherembodiment, the first anode is made of copper, and the second anode ismade of a material selected from iron, cobalt, and nickel. In anotherembodiment, the first anode is made of copper; the second anode is madeof a material selected from iron, cobalt, and nickel; and the thirdanode is made of a material selected from tungsten, molybdenum,tantalum, and titanium. In one embodiment, a single voltage is appliedto all three anodes which creates a current flow through the electrolytesolution to deposit metal ions on the cathode seed layer. In anotherembodiment, a first voltage is applied to the first anode, a secondvoltage is applied to the second anode, and a third voltage is appliedto the third anode, to create three current flows from the three anodesto the single seed layer cathode, so as to set the current and/or metalion flow rates at desired rates.

EXAMPLES

Cu—Ni—W ternary-plating was carried out in a 250 ml Hull cell at roomtemperature with Princeton Applied Research 273A Computer-ControlledPotentiostat/Galvanostat. The aqueous electrolyte solutions used were0.05˜0.15 M Cu(SO₄); 0.05˜0.15 M Ni SO₄; 0.125˜0.4 M Na₂WO₄; and 0.2 MNa₃Citrate. The current density used was 10˜20 mA/cm². The cathodes(working electrode) were 5×5 cm² and 1×5 cm² samples from a Cu (PVD seedlayer)/TaN/Ta/Si blanket test wafer. The anode (counter electrode) was aspiral Pt wire (diameter of 0.004 cm and length of 15 cm). The referenceelectrode was saturated Ag/AgCl. Chemical compositions of the platedfilms were measured with a Hitachi 4700 scanning electron microscope(SEM)/energy dispersive spectrometer (EDS) and verified with SecondaryIon Mass Spectrometry (SIMS). The crystal phase compositions of theplated films were measured with SIEMENS x-ray diffraction (XRD).Transmission electron microscope (TEM)/EDS analysis was carried out toinvestigate the distribution of W and Ni in Cu substrate. The effect ofpH value was also investigated. The pH value of the plating solution wasadjusted by adding H₂SO₄ and NaOH. The ternary-plated samples wereannealed 4 hours at 425° C. in a vacuum oven with a background ofnitrogen to protect the sample from oxidation.

The EDS spectra indicated that tungsten was successfully ternary-platedwith Cu—Ni. Tungsten and nickel concentrations in the plated films weremeasured with SEM/EDS as shown in FIG. 7. The detected EDS spectra areK_(α) (8 keV), K_(β) (8.9 keV) and L_(α) (0.93 keV) of copper, K_(α)(7.5 keV) of nickel, and K_(α) (0.53 keV) of oxygen, as well as M_(α)(1.77 keV) of tungsten, under an electron beam of 15 kV. Quantificationof copper, nickel, tungsten, and oxygen was carried out by comparingCu—K_(α), Ni—K_(α), W—M_(α), and O—K_(α) with standard referencessupplied with the Hitachi 4700 SEM/EDS software. Nickel and tungstenconcentrations in the plated films are shown in FIGS. 8 and 9.

Cu—Ni—W ternary-plating with (1) fixed [Ni] and various [W] solutionconcentrations and (2) fixed [W] and various [Ni] solutionconcentrations were carried out to establish the effect of solutionconcentrations on Ni and W concentrations in the plated films. Thequantitative analysis results of the EDS spectra indicate that: Withfixed [Ni] in solution [Ni] in the plated films decreases withincreasing [W] in solution, and [W] in the plated film does not changewith changing [W] in solution (see FIG. 8); and with fixed [W] insolution, [Ni] in the plated films increases with increasing [Ni] insolution, and [W] in the plated film does not appear to change withchanging [Ni] in solution (see FIG. 9).

Time-of-Flight Secondary Ion Mass Spectrometry (ToFSIMS) was used todetect tungsten and nickel in the Cu—Ni—W alloy plated samples afterbriefly sputtering with Ga⁺ to remove any surface oxides and organics.Profiles of tungsten and nickel concentrations versus depth from surfaceinto the films are shown in FIGS. 10 and 11. Tungsten has a maximumconcentration at the surface. Both tungsten and nickel concentrationsdecrease with depth of the plated film (see FIG. 10). TEM/EDS indicatethe existence of high concentration areas of tungsten. Annealing four(4) hours at 425° C. in N₂ improved the uniformity of nickel andtungsten distributions in the plated films (see FIG. 11). This mayresult from the diffusion of tungsten and nickel during the annealing.Since tungsten's high melting point and the atomic radius differencebetween tungsten and copper the diffusion of tungsten in copper at sucha low temperature is expected to be limited.

Transmission electron micrograph was taken of copper-nickel-tungstencoplated film after annealing 4 hours at 425° C. in vacuum oven with N₂.The plated film includes two types of phases with different densities.Small dark (higher density) crystalline phase in a dimension of about 10to 20 nm are widely dispersed within the amorphous matrix (lowerdensity). TEM/EDS spectra indicate that copper, 3 to 5% nickel, andoxygen exist all through the film. The crystalline grains contain mainlycopper, 3 to 5% nickel, oxygen, and a very small amount of tungsten. Theamorphous matrix contains no tungsten. Experiments with different pHvalues, but same copper, nickel and tungsten concentrations in thesolutions indicated that the pH value (6˜8) does not change nickel andtungsten concentrations in the plated films nor the resistivity of theplated films. But the surface brightness decreases with the decrease ofpH.

XRD spectra (FIG. 12) show only the spectra of pure copper, that is Cu(111) at 2θ=43.356°, Cu (200) at 2θ=50.496°, Cu (220) at 2θ=74.201°, andCu (311) at 2θ=90.360°, with Cu K_(α) (λ=1.5418 Å) radiation. Thisindicates that the co-plated tungsten and nickel were not interstitiallydissolved in the copper solid solution. Copper and nickel have similaratomic radii, 1.28 Å and 1.24 Å respectively. It is known that copperand nickel may form a continuous solid solution. While tungsten has anatomic radius of 1.41 Å, 10.15% larger than that of copper. So tungstenis very unlikely dissolved in copper, as can be seen in a Cu—W phasediagram. The fact that no spectrum shift to lower angle was seenconforms to this. Therefore tungsten was very likely distributed ongrain boundaries of copper-nickel alloy crystalline phase.

Resistivity versus nickel concentration of the Cu—Ni—W ternary-platedfilms is plotted in FIG. 6. It is shown that resistivity increases withthe increase of nickel concentration in the plated films. From the plotwe can get: The resistivity increase per atomic percent addition ofnickel in the plated films is approximately 1.3 μΩcm/at. %. With theexistence of an average of 1.4 at. % tungsten in the films, resistivityincreased about 2 μΩ cm compare to pure copper.

In the preceding detailed description, specific embodiments weredescribed. It will, however, be evident that various modifications andchanges may be made thereto without departing from the broader spiritand scope as set forth in the claims. The specification and drawingsare, accordingly, to be regarded in an illustrative rather than arestrictive sense.

1. A method comprising: providing a substrate, wherein the substratecomprises an interior of a multilayer interconnection structure;depositing a copper seed layer exterior to the substrate; andelectroplating a metal alloy layer comprising a group IB metal and amaterial selected from the group consisting of iron, cobalt, and nickel,the metal alloy layer exterior to the substrate, and exterior to thecopper seed layer.
 2. The method of claim 1, further comprising:depositing a barrier layer exterior to the substrate, and interior tothe conductive seed layer, and interior to the metal alloy layer,wherein the barrier layer is deposited prior to the depositing of theconductive seed layer.
 3. The method of claim 1, further comprising:coupling the metal alloy layer to a contact point of the substrate, thecontact point including at least one of a circuit device and a secondinterconnection.
 4. The method of claim 3, wherein the conductive seedlayer is coupled to the contact point; and wherein the metal alloy layeris coupled to the conductive seed layer.
 5. The method of claim 1,wherein the metal alloy layer comprises tungsten.
 6. The method of claim1, wherein the metal alloy layer comprises nickel, and tungsten.
 7. Themethod of claim 1, wherein the metal alloy layer comprises copper,nickel, and tungsten.
 8. The method of claim 1, wherein the metal alloycomprises: a first material selected from the group consisting of iron,cobalt, and nickel; and a second material selected from the groupconsisting of tungsten, molybdenum, tantalum, titanium, vanadium,niobium, yttrium, zirconium, ruthenium, palladium, halfnium, rhenium,and platinum.
 9. The method of claim 1, wherein the metal alloy layercomprises: copper; a first material selected from the group consistingof iron, cobalt, and nickel; and a second material selected from thegroup consisting of tungsten, molybdenum, tantalum, and titanium.
 10. Amethod comprising: transmitting an electronic signals to or from eachlayer of a multilayer interconnection structure comprising at leastthree elements formed on a substrate including a barrier layer, and aconductive seed layer, wherein the interconnection structure includes ametal alloy layer including a group IB metal and a material selectedfrom the group consisting of iron, cobalt, and nickel.
 11. The method ofclaim 10, further comprising: depositing a barrier layer exterior to thesubstrate, and interior to the conductive seed layer, and interior tothe metal alloy layer, wherein the barrier layer is deposited prior tothe depositing of the conductive seed layer.
 12. The method of claim 10,further comprising: coupling the metal alloy layer to a contact point ofthe substrate, the contact point including at least one of a circuitdevice and a second interconnection.
 13. The method of claim 12, whereinthe conductive seed layer is coupled to the contact point; and whereinthe metal alloy layer is coupled to the conductive seed layer.
 14. Themethod of claim 10, wherein the metal alloy layer comprises tungsten.15. The method of claim 10, wherein the metal alloy layer comprisesnickel, and tungsten.
 16. The method of claim 10, wherein the metalalloy layer comprises copper, nickel, and tungsten.
 17. The method ofclaim 10, wherein the metal alloy comprises: a first material selectedfrom the group consisting of iron, cobalt, and nickel; and a secondmaterial selected from the group consisting of tungsten, molybdenum,tantalum, titanium, vanadium, niobium, yttrium, zirconium, ruthenium,palladium, halfnium, rhenium, and platinum.
 18. The method of claim 10;wherein the metal alloy layer comprises: copper; a first materialselected from the group consisting of iron, cobalt, and nickel; and asecond material selected from the group consisting of tungsten,molybdenum, tantalum, and titanium.